[PATCH 2/3] gdb: New maintenance command to disable bfd sharing.

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

In some rare maintainer cases it is desirable to be able to disable bfd
sharing.  This patch adds new commands maintenance set/show commands for
bfd-sharing, allowing gdb's bfd cache to be turned off.

OK to apply?

Thanks,
Andrew

gdb/ChangeLog:

	* gdb_bfd.c (bfd_sharing): New variable.
	(gdb_bfd_open): Check bfd_sharing variable.
	(_initialize_gdb_bfd): Add new set/show command.
	* NEWS: Mention new command.
---
 gdb/ChangeLog |  7 +++++++
 gdb/NEWS      |  4 ++++
 gdb/gdb_bfd.c | 29 +++++++++++++++++++++++++----
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d79d8e3..291c1be 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2015-04-13  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* gdb_bfd.c (bfd_sharing): New variable.
+	(gdb_bfd_open): Check bfd_sharing variable.
+	(_initialize_gdb_bfd): Add new set/show command.
+	* NEWS: Mention new command.
+
+2015-04-13  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* gdb_bfd.c (struct gdb_bfd_data): Add size field.
 	(struct gdb_bfd_cache_search): Likewise.
 	(eq_bfd): Compare the size fields.
diff --git a/gdb/NEWS b/gdb/NEWS
index c24195e..673aca4 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -62,6 +62,10 @@ show max-completions
   to avoid generating large completion lists, the computation of
   which can cause the debugger to become temporarily unresponsive.
 
+maint set bfd-sharing
+maint show bfd-sharing
+  Control the reuse of bfd objects.
+
 maint set symbol-cache-size
 maint show symbol-cache-size
   Control the size of the symbol cache.
diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index 35c068f..48838cc 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -104,6 +104,11 @@ DEFINE_REGISTRY (bfd, GDB_BFD_DATA_ACCESSOR)
 
 static htab_t gdb_bfd_cache;
 
+/* When true gdb will reuse an existing bfd object if the filename,
+   modification time, and file size all match.  */
+
+static int bfd_sharing;
+
 /* The type of an object being looked up in gdb_bfd_cache.  We use
    htab's capability of storing one kind of object (BFD in this case)
    and using a different sort of object for searching.  */
@@ -389,7 +394,7 @@ gdb_bfd_open (const char *name, const char *target, int fd)
      opening the BFD may fail; and this would violate hashtab
      invariants.  */
   abfd = htab_find_with_hash (gdb_bfd_cache, &search, hash);
-  if (abfd != NULL)
+  if (bfd_sharing && abfd != NULL)
     {
       close (fd);
       gdb_bfd_ref (abfd);
@@ -400,9 +405,12 @@ gdb_bfd_open (const char *name, const char *target, int fd)
   if (abfd == NULL)
     return NULL;
 
-  slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
-  gdb_assert (!*slot);
-  *slot = abfd;
+  if (bfd_sharing)
+    {
+      slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
+      gdb_assert (!*slot);
+      *slot = abfd;
+    }
 
   gdb_bfd_ref (abfd);
   return abfd;
@@ -923,4 +931,17 @@ _initialize_gdb_bfd (void)
   add_cmd ("bfds", class_maintenance, maintenance_info_bfds, _("\
 List the BFDs that are currently open."),
 	   &maintenanceinfolist);
+
+  add_setshow_boolean_cmd ("bfd-sharing", no_class,
+			   &bfd_sharing, _("\
+Set whether gdb will share bfds that appear to be the same file."), _("\
+Show whether gdb will share bfds that appear to be the same file."), _("\
+Tells gdb whether to share bfds that appear to be the same file.  The\n\
+modification time and file size are used to determine if a file on\n\
+disc has changed."),
+			   NULL,
+			   NULL,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
+  bfd_sharing = 1;
 }
-- 
2.2.2